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Astron. Astrophys. 344, 483-493 (1999)

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1. Introduction

A large fraction of all spiral galaxies are barred systems, thus making barred galaxies an important class of galaxies. To increase our knowledge about these systems we need to understand both the dynamics of bars and the influence the bars have on the discs.

The appearance of a bar will inevitably change the dynamics of a galaxy. The bar will drastically reshape the central region affecting the orbits of the stars and moving the locations where gas clouds can exist and where star formation can take place (Athanassoula 1992; Sellwood & Wilkinson 1993; Kennicutt 1994). The effects of the bar will not be limited to the bar region, but will extend throughout the galaxy. The strong non-axisymmetric potential will perturb orbits far out and can drive spiral arm structure in the rest of the disc. Observational evidence also prove that the influence of the bar affects the chemical abundance gradients in barred galaxies (Vila-Costas & Edmunds 1992; Zaritsky et al. 1994; Martin & Roy 1994). This has also been seen in numerical studies of barred systems (Friedli & Benz 1995).

In this paper, we will study mass relocation occurring in galactic discs as a result of bar formation and evolution. To accomplish this, we have performed extended computer simulations using two-dimensional, stellar Kuzmin discs and fixed 3D-potentials. We have focused on changes in the surface density and the underlying causes and we will present a detailed discussion based on one of our simulations.

Sect. 2 will describe our simulation method while Sect. 3 will be devoted to a discussion on mass relocation caused by a bar. Finally, our main conclusions will then be summarised in Sect. 4.

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© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999